scholarly journals A Two-part Approach to the Determination of Intrinsic Rate Constants of an Alpha-amylase Catalysed Reaction

2020 ◽  
pp. 8-21
Author(s):  
Ikechukwu I. Udema
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Catalytic Efficiency ◽  
Intrinsic Rate ◽  
Product Formation ◽  
Intermolecular Potential ◽  
Diffusion Controlled ◽  
Quantitative Results ◽  
Intrinsic Rate Constant

Background: There is a need for equations with which to calculate the intrinsic rate constants that can further characterise enzyme catalysed reactions despite what seems to be conventional differences in methodology in the literature. Methods: Theoretical, experimental (Bernfeld method), and computational methods. Objectives: 1) To derive an alternative intrinsic rate constant equations consistent with their dimension, 2) derive electrostatic intermolecular potential energy equation, (xe), 3) calculate the intrinsic rate constants for forward (k1) and reverse (k2) reactions, and 4) define the dependence or otherwise of kinetic constants on diffusion and deduce the catalytic efficiency. Results and Discussion: The ultimate quantitative results were ~ 64.69 ±  0.49 exp (+3)/ min (k2) (and kd (s) = ~ 60.66 exp (+3)/ min), ~ 1594.48 ± 11.99 exp (+3) exp (+3) L/mol.min (k1) (and ka (s) = ~1482.47 exp (+3) L/mol.min), ~ 58.00 ± 10.83 exp (+3) /min, the apparent rate constant for reverse reaction (kb), and ~ 75.83 ± 10.83 exp (+3) /min, the rate constant for product formation (k3). The catalytic efficiency was: 3.025 exp (+ 9) L / mol.     Conclusion: The relevant equations were derived. Based on the derived equations the intrinsic rate constants can be calculated. Since k3 is > kb, then k3 is diffusion controlled and it appears that the enzyme has reached kinetic perfection. The evaluation of rate constants either from the perspective of diffusion dependency or independency cannot be valid without Avogadro number.

Carbanion reactivity — σ-adduct formation and elimination in the reactions of the carbanion from bis(phenylsulfonyl)methane with 4-nitrobenzofurazan derivatives

2008 ◽  
Vol 86 (3) ◽  
pp. 225-229 ◽  
Author(s):  
Basim H.M. Asghar ◽  
Michael R Crampton ◽  
Chukwuemeka Isanbor
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Intrinsic Rate ◽  
Adduct Formation ◽  
Nmr Studies ◽  
H Nmr ◽  
A Value ◽  
Elimination Reactions ◽  
Intrinsic Rate Constant

1H NMR studies in [2H6]-DMSO show that the carbanion 4 from bis(phenylsulfonyl)methane reacts with 4,6-dinitrobenzofuroxan to yield a σ-adduct that undergoes base-catalysed elimination to yield an alkene derivative. Rate constants, measured spectrophotometrically, are reported for the corresponding reactions in methanol of 4 with 4-nitrobenzofurazan and some derivatives that give adducts at the 5-position. The intrinsic rate constant, ko, for this process has a value of 1.5 ± 0.5. The 5-adducts undergo methoxide-catalysed elimination of phenylsulfinic acid to yield alkene derivatives and rate constants for this process are reported.Key words: carbanions, 4-nitrobenzofurazan, σ-adducts, elimination reactions.

Determination of rate constants of redox reactions of second order from current-less potential-time curves by a simplified graphical-numerical method

1983 ◽  
Vol 48 (5) ◽  
pp. 1358-1367 ◽  
Author(s):  
Antonín Tockstein ◽  
František Skopal
Keyword(s):  
Numerical Method ◽  
Explicit Form ◽  
Rate Constant ◽  
Optimization Algorithm ◽  
Rate Constants ◽  
Redox Reactions ◽  
Second Order ◽  
Wide Region ◽  
Recurrent Formula

A method for constructing curves is proposed that are linear in a wide region and from whose slopes it is possible to determine the rate constant, if a parameter, θ, is calculated numerically from a rapidly converging recurrent formula or from its explicit form. The values of rate constants and parameter θ thus simply found are compared with those found by an optimization algorithm on a computer; the deviations do not exceed ±10%.

scholarly journals Effect of Vascular Activity in the Determination of Rate Constants for the Uptake of 18F-Labeled 2-Fluoro-2-Deoxy-D-Glucose: Error Analysis and Normal Values in Older Subjects

1986 ◽  
Vol 6 (6) ◽  
pp. 724-738 ◽  
Author(s):  
A. C. Evans ◽  
M. Diksic ◽  
Y. L. Yamamoto ◽  
A. Kato ◽  
A. Dagher ◽  
...  
Keyword(s):  
Rate Constant ◽  
Gray Matter ◽  
Rate Constants ◽  
Cerebral Blood Volume ◽  
Physiological State ◽  
Control Group ◽  
Vascular Activity ◽  
Regional Cerebral Blood Volume ◽  
Wide Range

Regional cerebral blood volume (CBV) can be calculated using data obtained during the kinetic analysis of 18F-labeled 2-fluoro-2-deoxy-d-glucose (FDG) uptake measured by positron emission tomography (PET). As a result the influence of vascular activity upon the determination of FDG rate constants can be minimized. The method is investigated by simulation experiments and by analysis of PET studies on seven older, healthy human volunteers aged 52–70 years. The accuracy of measured FDG rate constants k1, k2, and k3, obtained either by omitting the early portion of the uptake curve or by explicit inclusion of CBV as a fit parameter, is compared. The root mean square error in measured rate constant for the latter method is equivalent to that obtained by omitting the first 2.5–3 min of tissue data and neglecting the CBV term. Hence, added information about the physiological state of the tissue is obtained without compromising the accuracy of the (FDG) rate constant measurement. In hyperemic tissue the explicit determination of the vascular fraction results in more accurate estimates of the FDG rate constants. The ratio of CBV determined by this method to CBV obtained using C15O in six subjects with CBV in the normal range was 0.92 ± 0.32. A comparison of the CBV image obtained by this method with that obtained using C15O in an arteriovenous malformation case demonstrates the accuracy of the approach over a wide range of CBV values. The mean value for CBV fraction in gray matter obtained by this method in the older control group was 0.040 ± 0.014. Average gray matter rate constants obtained were k1 = 0.084 ± 0.012, k2 = 0.150 ± 0.071, and k3 = 0.099 ± 0.045 min−1.

scholarly journals Kinetic Study of CaCO3 Precipitation Accelerated by High Voltage Impulse

2021 ◽  
Vol 43 (2) ◽  
pp. 125-134
Author(s):  
Damha Kim ◽  
In-Soung Chang
Keyword(s):  
Rate Constant ◽  
High Voltage ◽  
Rate Constants ◽  
Reaction Order ◽  
Reaction Rate Constant ◽  
Formation Reaction ◽  
Different Temperatures ◽  
Synthetic Solution ◽  
Scale Control

Objectives : Determination of reaction order (n) and rate constants (k) of the CaCO<sub>3</sub> scale formation reaction that was accelerated by the HVI (high voltage impulse) induction.Methods : HVI was inducted to the synthetic solution containing 2.5 mM of Ca<sup>2+</sup> ion at different temperatures of 25, 40, 60℃. The concentration of Ca<sup>2+</sup> ion has been monitored as voltages of the HVI increased from 0 to 5, 10, 15 kV. Reaction order and the rate constants of the CaCO<sub>3</sub> formation reaction were determined with the experimental dataset of Ca<sup>2+</sup> concentration vs. time plots.Results and Discussion : The CaCO<sub>3</sub> formation was determined to follow two-molecules 2<sup>nd</sup> order reaction. The reaction rate constant, k increased as temperature and the applied voltages of HVI increased. The rate constant, k at 25℃ and 15 kV of HVI was 8.2×10<sup>-3</sup> L/(mmol･hr), which was 2.7 times greater than the k of the control at 25℃, 3.0×10<sup>-3</sup> L/(mmol･hr).Conclusions : The reaction of CaCO<sub>3</sub> formation was accelerated by HVI as the applied voltages of HVI increased, indicating that the HVI could be used as an alternative desalting technology for scale control.

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